All motor vehicles include a control for switching between high beam and low beam operation of the motor vehicle headlamps. This control may be implemented by a floor mounted switch but most typically in more recent designed motor vehicles is implemented with a stalk on the vehicle steering column that is easily actuated by a motor vehicle operator.
When the high beam option is selected, the vehicle headlamps are focused in a direction that illuminates further in advance of the vehicle to improve a motorist's ability to see details in his or her line of sight. When an oncoming vehicle approaches, the motorist can switch to low beam operation to avoid temporarily blinding the oncoming driver. Fog lamps are occasionally installed on vehicles to direct a lamp output downward in a direction closer to the vehicle to enable the motorist to more clearly see during rain and foggy conditions.
Vehicle head lamps most typically contain two separate light bulbs that can be independently activated. When one of the bulbs is activated, a low beam lamp output is produced and when a second bulb of the two bulbs is activated a high beam lamp output is provided. In the 1980's when headlamps having halogen light bulbs were first built, the government enacted photometric tests. These tests dictated that light of a high enough intensity to cause spot blindness in other motorists did not reach certain regions in a space in front of a motor vehicle headlamp. Spot blindness was only a problem for halogen lights since these lights produce a much more intense output when compared with non-halogen lamps.
U.S. Pat. No. 5,517,389 to Meyers concerns an electrochromic lamp assembly including a reflector having two or more reflective surfaces. A light source and an electrochromic means is positioned between the light source and at least one reflective surface. Each reflective surface directs light in a different direction. The electrochromic means is capable of blocking light from exiting the lamp assembly from at least one direction.